This invention relates to photographic apparatus and, more particularly, to an improved apparatus for automatically operating a multipurpose film handling cassette through preprogrammed sequences, for both processing and projection.
Cinamatographic systems employing a programmable viewing apparatus and multipurpose cassette containing a film strip together with a supply of processing fluid so that the film strip may be exposed in a camera and subsequently processed and projected in the programmable viewing apparatus are the subject of several issued U.S. patents and pending applications commonly assigned to the assignee of the present invention. For example, U.S. Pat. No. 3,851,958, issued to Edwin H. Land on Dec. 3, 1974, describes a multipurpose cassette, and motion picture system, while U.S. Pat. No. 3,895,862 issued on July 22, 1975 to Joseph A. Stella et al., is directed to a cassette arrangement for the above-noted system.
In the system described in the above-noted patents, a strip of film, as supplied with the cassette, is initially wound on a supply spool and advanced to a takeup spool when the cassette is placed in an appropriate camera for exposure in an essentially conventional fashion. After exposure, the cassette is placed into a viewing apparatus capable of activating a cassette-contained processor to deposit a uniform layer or coating of processing fluid along the length of the film strip as it is rewound from the takeup spool back to the supply spool. Thereafter, the series of successive transparent image frames formed on the film strip may be viewed by projection and rewound for subsequent projection cycles as desired. In the current state of the art, successive convolutions of the film strip wound on the cassette takeup or supply spool are separated by a pair of parallel raised "rails" extending along the longitudinal margins or edges of the film strip. When the processing fluid has been deposited on the emulsion surface of the film strip and the wet film has been wound on the supply spool, the rails serve to space successive convolutions or layers sufficiently so that no mechanical contact is made with the wet emulsion. However, if the film is wound too tightly on the supply spool, successive convolutions of the film may be drawn into contact despite the rails and produce undesirable transfer patterns on the processed positive transparency. Consequently, it is important that the film strip not be wound too tightly on the supply spool during the period following deposition of processing fluid on the film. Further, such "cinching" of the film strip during subsequent rewinds of the processed film strip has also been found to be potentially detrimental to the quality of the processed positive transparency and accordingly is considered undesirable.
U.S. Pat. No. 3,851,958, entitled "PHOTOGRAPHIC SYSTEM FOR PROCESSING AND PROJECTING TRANSPARENCIES" cited hereinabove, describes a system for sensing the termination of film strip travel at the end of rewind and for shutting off the drive motor and ejecting the cassette from the viewing apparatus. In such a system, use is made of an existing "jam sensor" circuit which is designed to sense termination of rotation of the takeup reel drive shaft in the viewer and upon cessation of such rotation for a predetermined time will cause a signal to occur which initiates motor shut off and ejection of the cassette from the viewer. In order to avoid accidental generation of this signal, the time constant selected is relatively long, i.e., it has typically been on the order of three seconds. Accordingly, since this same system has been used for ejection of the cassette at the termination of rewind, the film strip has been potentially subjected to three seconds of "cinching" at the end of rewind following each projection cycle.